Hi John

The water resistance stated on the watch is the maximum that the manufacturer can be held accountable for which means if it does fail they will only cover it under warranty if it has been used within the ISO rating declared by the manufacturer (ISO22810 and ISO6425). However this doesn’t stop the watch being built better than declared and Casio are one manufacturer who regularly exceed build better than they say. However if the water resistance of any watch fails it will only be covered by how the manufacturer ‘warrants’ the watch by its design.

I used the stopwatch underwater to time how long I could stay down there.

It never failed and that was despite me using the stopwatch and light many times over 2 years at the bottom of different pools (on different vacations) and showering with it still on daily.

I think that’s an excellent point! All too often people expect a watch to perform as well as it did the day it was purchased and while the rubber seals can be replaced, it’s a whole other story if the the metal surface has become compromised. This is why it’s really important to get the seals checked periodically.